Anticorrosive for lubricants

ABSTRACT

Lubricants can be combined with an anticorrosive consisting of from 67 to 99 percent by weight of an alkaline earth metal petroleum sulfonate and/or an oil-soluble alkaline earth metal salt of a fatty acid having from 10 to 36 carbon atoms, and/or an oil-soluble alkaline earth metal salt of an alkyl-sulfamidocarboxylic acid, and from 33 to 1 percent by weight of benzotriazol.

United States Patent Inventors Gunter Koenig;

Helmut Landau, both of Gersthofen, Germany App1.No. 721,619

Filed Apr. 16, 1968 Patented Dec. 7, 1971 Assignee Farbwerke l-loechst Aktiengesellschaft vormals Melster Lucius 8r Bruning Frankfurt am Main, Germany Priority May 13, 1967 Germany F 52402 ANTICORROSIVE FOR LUBRICANTS [56] References Cited UNITED STATES PATENTS 2,610,946 9/1952 Eckert 252/33.3 2,814,594 11/1957 Smite 252/33.3 2,890,170 6/1959 Ragborg 252/50 2,908,648 10/1959 Spivack et a1. 252/47.5 3,352,780 11/1967 Groslambert 252/33.3 FOREIGN PATENTS 793,115 4/1958 Great Britain 252/50 Primary Examiner-Daniel E. Wyman Assistant Examiner-l. Vaughn Attorney-Connolly and Hutz ABSTRACT: Lubricants can be combined with an anticorrosive consisting of from 67 to 99 percent by weight of an alkaline earth metal petroleum sulfonate and/or an oil-soluble alkaline earth metal salt of a fatty acid having from 10 to 36 carbon atoms, and/or an oil-soluble alkaline earth metal salt of an alkyl-sulfamido-carboxylic acid, and from 33 to 1 percent by weight of benzotriazol.

ANTICORROSIVE FOR LUBRICANTS The present invention provides an anticorrosive for use in lubricants, especially those lubricants which contain as extreme pressure agents compounds of chlorine, sulfur or phosphorus.

It is indispensible to add anticorrosives to modern extreme pressure lubricants and highly stressed mineral oils, and numerous substances have already been proposed for this purpose. The problem to be solved consists in choosing an anticorrosive that meets the following requirements: on the one hand, it has to prevent all undesired corrosions from the machine parts coming into contact with the lubricant and, on the other hand, it must not adversely affect the lubricating effect. Especially when additives containing chlorine are used as an extreme pressure agent, it can be observed again and again that even those machine parts which are not under load, show signs of corrosion.

Almost the same applies to extreme pressure additives containing active sulfur, as well as to some phosphorus compounds. These undesired side effects limit the use of these otherwise highly effective additives to those cases in which the lubricant is not exposed in the oil sump to temperatures exceeding 80 C., Le. generally to cutting oils to be used for metal processing and mildly doped industrial gear oils.

The aforesaid signs of corrosion can be avoided, when the lubricants mentioned are used, as it is known for a long time and disclosed, for example, in German Pat. No. 1,1 15,395 laid open to public inspection, by adding alkaline earth metal petroleum sulfonates, especially calcium and barium petroleum sulfonates, which must, however, be added in relatively high amounts. For example, when one to two parts by weight of a barium petroleum sulfonate having a barium content of about 7 percent, are added to I parts by weight of a lubricant consisting of 10 percent by weight of a chlorinated paraffin (60 percent of chlorine) and 90 percent by weight of mineral oil (usual lubricating oil according to German lndustrial Standards (DIN) 51 501 a sufficient protection against the corrosion of an antifriction bearing steel (105 Cr and deep-drawing metal sheet is obtained up to a temperature of 100 C. This protection is, however, only assured as far as the lubricant is not penetrated by water. Another drawback inherent in the use of such a lubricant resides in the fact that the extreme pressure properties of the additive (in the present case: chloroparaffin) are reduced considerably by the high concentration of the petroleum sulfonate. For example, the aforesaid lubricant without an anticorrosive assured an undamaged running, when tested in the gear rig by the FZG- method A 8.3/90 according to DlN 51 354, up to the llth load step whereas the same lubricant to which 1 percent by weight of barium petroleum sulfonate had been added, already caused damage at the ninth load step. Also in the fourball apparatus according to Shell-Boerlage, a reduction of the seizure load by two to three load steps can be established, as compared with the lubricant without an addition of petroleum sulfonate. The petroleum sulfonates of the other alkaline earth metals behave in a similar way, but their anticorrosive effect is weaker than that of the barium compounds.

We have now found that mixtures comprising from 67 to 99 percent by weight of an alkaline earth metal petroleum sulfonate and/or an oil-soluble alkaline earth metal salt of a fatty acid containing from to 36 carbon atoms, and/or an oilsoluble alkaline earth metal salt of an alkyl-sulfamido-carboxylic acid and from 33 to 1 percent by weight of benzotriazol, can advantageously be used as anticorrosives in lubricants.

After benzotriazol has been used for a long time as an anticorrosive especially for nonferrous metals while it has, however, been known that this compound has not a noticeable anticorrosive effect on steel, it was surprising and not at all expected that a practically complete protection against corrosion can be obtained by adding the combinations of the invention to lubricants of the aforesaid composition as well as to mineral oils that have to stand extreme temperatures, for example turbine oils. It is furthermore surprising that already a very low concentration of the components to be added is suffcient to achieve a complete protection, a fact that points to a pronounced synergism. For example, when 0. l part by weight of a mixture of 10 parts by weight of a barium petroleum sulfonate containing 7 percent of barium, and 1 part by weight of benzotriazol are added to I00 parts by weight of a mineral oil having an additive of 25 percent of chloroparafiin 60 percent of chlorine), all usual corrosion tests reveal that unalloyed and alloyed steels as well as nonferrous metals are completely protected against corrosion up to a temperature of about 170 C. and, even when from 1 to 2 percent of water are present in the lubricant, no corrosion can be observed.

By alkaline earth metal petroleum sulfonates there are understood hereinafter commercial oil-soluble salts of alkaline earth metal oxides or hydroxides and petroleum sulfonic acids as, for example, obtained by the refining of crude mineral oils with sulfuric acid, oleum, chlorosulfonic acid or S0 and which, from the viewpoint of chemistry, represent an indefinable mixture of aliphatic and cyclic sulfonates with alkyl-arylsulfonates. Barium petroleum sulfonates having a barium content in the range of from 4 to 10 percent by weight, have proved to be particularly suitable. Oil-soluble alkaline earth metal salts of fatty acids containing from 10 to 36 carbon atoms, or the mixtures of such acids, for example salts of lauric acid, ricinoleic acid, palm oil fatty acid, behenic acid and montanic acid, can also be used, although they do not yield the same good results. The barium salts are preferred. it is, moreover, possible to use the oil-soluble alkaline earth metal salts, preferably the barium salts, of alkyl-sulfamido-carboxylic acids of the formula R'SO=NH(CH,),,'COOH, in which R represents a hydrocarbon radical having from about 10 to l8, preferably 13 or 14, carbon atoms and n represents an integer of from 1 to 5; salts in which n is 1 being especially mentioned. The aforesaid substances may be combined either as such or in mixture with benzotriazol.

The anticorrosive combinations of the invention containing, per 100 parts by weight, from 67 to 99 parts by weight of the oil-soluble alkaline earth metal salts and correspondingly from 33 to one parts by weight of benzotriazol, are prepared by dissolving the benzotriazol in the molten alkaline earth metal salts. Generally, they are incorporated into the lubricants to be protected in amounts ranging from 0.1 to 2, preferably from 0.25 to 1, percent by weight, calculated on the total amount of lubricant.

The following example serves to illustrate the present invention, but is not intended to limit it thereto, the parts being by weight unless stated otherwise.

EXAMPLE An anticorrosive was prepared by dissolving 1.0 part of benzotriazol in l0.0 parts of a barium petroleum sulfonate (7 percent of Ba) that had been heated to C. Subsequently, 0.25 part of this mixture was incorporated into a lubricant consisting of 74.75 parts of mineral oil (of a naphthenic base, viscosity class SAE, and 25.00 parts of chloroparafiin containing 60 percent by weight of chlorine. For testing the anticorrosive effect, an emulsion was mechanically prepared from parts of this mixture and one part of water.

A deep-drawing metal sheet strip (l.5 20 0.l centimeters), an antifriction bearing ball (one-half inch in diameter, steel Cr 5), a copper sheet strip (5XlXO.l centimeters) and a brass sheet strip (5XlX0.l centimeters) were then immersed in grams of the lubricant thus treated. The deepdrawing metal sheet was brought into direct contact with the ball and the whole arrangement was put in a heating cabinet at l00 C. for 100 hours. After the testing time, no signs of corrosion could be detected on any of the metals used.

In comparative tests using the lubricant without the anticorrosive, the ferrous metals were strongly attached over the whole portion immersed, partially with pitting. The nonferrous metals were distinctly attached. An addition of 2.5 parts of the barium petroleum sulfonate instead of corrosion as the barium petroleum sulfonate caused a reduction of the load-carrying capacity tested by the FZG-method by two steps and a reduction of the seizure load in the four-ball apparatus by two load steps. As a comparative sample there was used the noninhibited lubricant.

What is claimed is:

l. A lubricating composition consisting of mineral oil and an extreme pressure amount of chlorinated parafi'm and containing synergistic anticorrosion proportions of barium petroleum sulfonate and benzotriazol.

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